1. Field of the Invention
The present invention relates to a processing equipment of a single substrate transfer type for cleaning and drying a substrate, e.g., a silicon wafer, a compound semiconductor wafer, a glass substrate for a liquid crystal display, a metal substrate, or the like, one by one.
2. Description of Related Art
Conventionally, a wafer cleaning apparatus comprising a pure water jet device for jetting a cleaning liquid such as pure water to which ultrasonic wave is applied, wherein a wafer is cleaned by passing through pure water jetted from the pure water jet device, is known, as described in Japanese Patent Application Laid-Open Publication No. Hei-3-93230.
Such a kind of ultrasonic cleaning apparatus is used, for example, for removing fine particles, dusts or the like on a wafer. The ultrasonic cleaning apparatus generates longitudinal pressure waves in pure water by ultrasonic vibration. The pressure waves having an energy reaches to the surface of the wafer through the pure water and strike the particles attached to the surface of the wafer several hundreds of thousands times every second by the energy, to remove the particles from the wafer surface.
However, such a conventional ultrasonic cleaning apparatus has following problems.
Since such a kind of ultrasonic cleaning apparatus does not reuse the pure water which was jetted from the pure water jet device, processing of a lot of wafers requires a large quantity of pure water, and therefore, costs for cleaning enormously increases. In order to enhance cleaning effect, it is necessary to properly maintain the temperature of the pure water. Maintenance of the proper temperature requires installation of a heat exchanger for exchanging heat between the pure water and cooling water, in the pure water jet device, the pure water supply system or the like. However, the installation of the heat exchanger in the pure water jet device exerts adverse effect on propagation of the ultrasonic wave therein. In order to avoid such adverse effect, it is necessary to provide a large-sized pure water jet device and to arrange the heat exchanger at a position in an area of the inside of the jet device which exerts no adverse effect on propagation of the ultrasonic wave.